Proximity warning transmitter for emergency vehicles

ABSTRACT

A transmitter, carried by an emergency vehicle, transmits directional jamming radiation to operating receivers of passenger vehicles in its path. Different fixed frequency audio signals alternately modulate both an AM carrier and an FM carrier to provide a wobbling sound at either AM or FM receivers. The carrier frequencies are varied through their respective broadcast bands to scan up and down their frequency spectrums so that the alarm is picked up by any receivers in the directional path of radiation regardless of the station to which it is turned. The carriers are caused to scan their broadcast spectrums by imparting reciprocating motion to slugs in inductor tuners in circuit with the respective oscillators, thereby varying the carrier frequencies.

United States Patent 51 3,660,8 1 1 Vail et al. 1 May 2, 1972 s41PROXIMITY WARNING TRANSMITTER 2,490,591 12/1949 l-limmer ..331/1s1 x FOREMERGENCY VEHICLES 1,612,427 12/1926 Flurscheim.. .....340/33 UX2,605,393 7 1952 Holm ..340 34 UX [72] Inventors: Evelyn W. Vail; JohnPopik, both of l Columbus Primary Examiner-David L. Trafton [73]Assignee: Alert, Inc., Columbus, Ga. Attorney-Wilkinson, Mawhinney &Theibault [22] F11ed: Nov. 12, 1.969 [57] ABSTRACT [21] Appl' 87s668 Atransmitter, carried by an emergency vehicle, transmits directionaljamming radiation to operating receivers of pas- [52] U.S.Cl..340/33,325/ 132,331/ 181, senger vehicles in its path. Different fixedfrequency audio 332/41 signals alternately modulate both an AM carrierand an FM lllt. carrier [o p ovide a sound at either or [58] Field ofSearch ..340/32,33, 34,384 E; receivers. The carrier frequencies arevaried through their 325/13 11 331/181; 332/41 respective broadcastbands to scan up and down their frequency spectrums so that the alarm ispicked up by any receivers in [56] References Cited the directional pathof radiation regardless of the station to UNITED STATES PATENTS which itis turned. The carriers are caused to scan their broadcast spectrums byimparting reciprocating motion to slugs in 2,465,341 3/1949 Altovsky..325/ 132 X inductor tuners in circuit with the respective oscillatorsGossler ....340/34 X thereby varying the carrier frequencies 2,994,7658/1961 Adam .325/131 X 2,910,688 /1959 Kelley et a1 ..340/384 E 6Claims, 4 Drawing Figures i 18 g 39011. m 1T 1 AUDIO |2;4-2m1-| NRY y 15 1"- osc. 3' 4s 22! 1ooo- 1 H050 L m ri L U a: 1 f o 33 '9 1 37 u fd.+12Vo a' 5 s 5H 5 1 l7 '5 3 0: I 47 j 5 2 g 33 g 1 luf AUDIO U 3 056. Losc. cow-4m 3000- HENRY 'PATENTEDMAY 2:912 3,660,811 SHEET 2 [IF 2 F IG.3 INVENTORS EVELYN W. VAIL JOHN POPIK ATTORNEYS- of vehicles of theproximity of an emergency vehicle in sufficient time to preventcollision.

Not only are a greater percentage of new vehicles being equipped withairconditioning but also the sound-proofing qualities of new cars arebeing improved. Thus, the greatest hazard is presented to persons ridingin those vehicles with the windows closed, either the air conditioningor heating equipment operating and the radio receiver'turned on.Regardless of the mode of receiver operation, i.e. AM or FM, and thesetting of the dial, it is the purpose of this invention to develop awarning audio signal at such receivers, which signal jams theentertainment broadcast to alert the driver to the presence of theemergency vehicle. Naturally, this signal will reach only the operatingradios within the directional range predetermined for the transmitter,usually a transmission path approximating the width of the street, sayfifty feet, and directed ahead of the vehicle for some distance, say 900to 1,000 feet, as developed from a 2 watt power output, therebyachieving its purpose without causing undue interference to neighborhoodentertainment sets.

A relatively inexpensive transmitter fulfilling these requirements maybe constructed by employing two or more sources of audio signals atdifferent fixed frequencies for selective or alternate modulation of theAM and FM carriers, by way of a single bistable multivibrator.

The FM and AM carrier oscillators are in circuit respectively withinductor tuners each of which has its reactance changed by the insertionor withdrawal of a magnetic or iron slug. Here, also, a single drivingmeans may be employed to drive both slugs in and out of their respectiveinductors to cause the carriers to scan their respective broadcast orentertainment spectrums. The varying frequency modulated carriers arerespectively amplified in suitable linear amplifiers and applied tobroadly tuned resonant'circuits respectively coupled to AM and FMantennas, each partly shielded to provide for directional radiation,generally along a path directly ahead of the emergency vehicle.

With the foregoing in mind, it is among the objects of this invention toprovide a proximity warning device effective through the operatingradioreceivers of automobiles in the path of emergency vehicles.

It is another object of the invention to provide such alarm? ing for AMreceivers, or for FM receivers, or for both simultaneously.

A further object of the invention is the provision of a wobble or warbletype audio broadcast signal, through the use of two or more fixed audiooscillators, for modulation onto AM and/or FM carriers.

Still another object is the provision of a bistable multivibrator forselectively applying the different audio signals to an FM, an AM, orboth types of carriers to provide carrier modulation.

Yet another object is the provision of a proximity warning transmitterwherein the carrier or carriers are varied in frequency back and forthacross their respective broadcast bands.

Another object of the invention is the provision of an emergency warningtransmitter equipped with directional antennas for confining radiationto a predetermined path.

The invention will now be described in connection with a preferredembodiment, as shown in the attached drawings, wherein:

FIG. 1 is a circuit diagram of an AM and FM transmitter to be carried byan emergency vehicle,

FIG. 2 is a schematic electromechanical arrangement for varying thefrequency of the carriers,

FIG. 3 is a view in perspective of the AM and FM antennas relative to ahousing therefor, and

FIG. 4 is a bottom view of the structure of FIG. 3.

Referring now to FIG. 1, the 12 volt vehicle power system is shown aspositive terminal 11 and negative terminal 13. A pair of fixed frequencyaudio oscillators 15 and 17 are connected to positive lead 19 overbranch leads 21 and 22 to supply their outputs to a bistablemultivibrator 23 over output leads 25 and 27. The multivibrator 23receives its positive voltage from lead 21 over lead 29 and provides anoutput over lead 31 to the primary winding 3 of transformer T Thesecondary winding 35 of transformer T is center tapped to ground at 37,and each end feeds a separate oscillator, shown at 39 and 41.

The upper oscillator 39 is provided to develop the FM carrier, and thelower oscillator 41 produces the AM carrier.

In series with FM oscillator 39, there is connected an inductor tuner L,and an isolation capacitor 43 with the output circuit extending to thevoltage divider comprising resistors 45 and 47.

Similarly, in series with the AM oscillator, there is connected theinductor tuner L and these tuners are preferably ganged together, asshown by the dotted line 51. The inductor tuners cause the modulatedcarriers to scan their respective entertainment broadcast bands, as willbe explained-in detail in FIG. 2. The carriers are introduced to theirrespective RF and IF frequency amplifiers, contained in the integratedcircuit 55, which is of General Electric type PA 273A. The amplifiedoutputs are introduced to the broad tuned resonant circuits 61 and 63for coupling to the FM antenna 65 over output transformer T and to theAM antenna 67 over output transformer 63, respectively.

The values of the various components are given in the circuit diagramsof FIG. 1, and the integrated circuits are identified as follows:

l5-= General Electric audio oscillator type PA 273 set for 1,000 cyclesper second.

17 General Electric audio oscillator type PA 273, set for afrequency.of-3,000 cycles per second.

23 General Electric type .IK fiip flop connected as a bistablemultivibrator.

39 Cordover type FMM-2.

41 Cordover type WM-S.

55 General Electric type PA 273A amplifier sections.

T 1:4 turns.

T 1:10 turns.

In operation, the fixed frequency oscillators 15 and 17 arealternatively modulated onto the AM and FM carriers at oscillators 41and 39. It is the change from the 1,000 cycle fixed frequency ofoscillator 15 to the 3,000 cycle per second tone of oscillator 17 andback, etc., which causes the audio wobble,

warble, or rising and falling tone in the listeners receiver to invitiate instant apprehension or alarm.

Next, the FM carrier of oscillator 39 is caused to scan its band, i.e.88 megacycles to 108 megacycles, because the iron slug 71 (FIG. 2) iscaused to move within and without inductor L Similarly, the AM carrierof oscillator 41 is caused to scan its broadcast band of 0.6 megacyclesto 1.5 megacycles as the iron slug 73 traverses inductor L The ironslugs 71 and 73 are connected together by rack 75 which carries stops 77and 79, and is reciprocated by pinion 81 driven over shaft 83 from motor85.

The stops 77 and 79 operate the fixed toggle switch 87, shown in dottedoutline, because it is the same switch as the double throw double polereversing switch 87, connected between the power terminals 11 13 andmotor 85.

When the motor is driven to the full forward position (as shown), theswitch blades 91 are spring biassed or toggle closed to the right andthe positive lead 11 is extended to the upper lead 93 for the DC motor85. However, at this time, stop 77 trips the toggle 87 so that theblades 91 are spring biassed or toggle closed to the left, and thenegative potential from lead 13 is now extended to motor lead 93, toreverse the movement until stop 79 toggles switch 87. Motor is of theinstantly rever'sable type, and the repeated action obtained serves tocause both carriers continually to scan up and down their broadcastbands. Adjustment of the spacing a location of stops 77 and 79 willcontrol the extent of scan, i.e. change of carrier frequencies.

In order that a relatively lower power of eg 2 or 3 watts may sufficefor the transmitter of FIG. 1 to avoid undue interference with apartmentor home receivers in the vicinity of the emergency vehicle, the antennas65 and 67 are partially shielded bythe slotted metal cylinders 65 and67' of FIGS. 3 and 4, thereby directing the radiation forward of theemergency vehicle and in a relatively narrow path. The housing 101 forthe antennas may be comprised of fiberglass or the like, and it isbolted or otherwise afiixed to the body of the emergency vehicle (seebolt or screw holes 103 and 105). The antennas 65 and 67. however, aregrounded to the metal or frame work of the emergency vehicle and arebest supported on top of a fender, toward the forward end of thevehicle.

It should be mentioned that the invention may similarly find applicationon the waterways or airways, particularlywhen fog or occludingconditions prevail, with appropriate frequency bands taken intoconsideration, of course, and perhaps broader directional radiationsprovided. It might also be mentioned that when the tuner passes throughthe higher police bands or other important bands, the transmittercircuit may be modulated to acceptable side tone only so as to preservevoice communications. Also, it may be possible to interrupt evenstereo-type players in vehicles, provided the manufacturers willcooperate by including an inexpensive tone receiver circuit within theamplifier circuits.

What is claimed is:

l. A proximity warning transmitter to be carried by an emergency vehiclefor transmission to conventional vehicle receivers comprising, incombination means for generating two conventional carriers of differentfrequencies; means for modulating one of the conventional carriers withaudio signals; means for modulating the other of said conventionalcarriers with said audio signals but in a different fashion; means forvarying the frequency of each conventional carrier throughout adifferent band of frequencies; and means for transmitting the modulatedvarying frequency carriers in a like predetermined direction relative tothe emergency vehicle.

2. The proximity warning transmitter of claim 1 wherein the means formodulating the conventional carriers comprises two separate sources ofdifferent frequency audio signals; and

switching means for alternately applying signals from said separatesources to modulate the conventional carriers and produce detectibleaudio warble carried by each.

3. The warning transmitter of claim 2 wherein the means for modulatingsaid one conventional carrier comprises amplitude modulating means; themeans for modulating said other conventional carrier comprises frequencymodulating means; and said switching means comprises bi-stablemultivibrator means.

4. The transmitter of claim 1 wherein the means for varying thefrequency of said one conventional carrier throughout a band offrequencies comprises an inductor tuner in circuit with the means forgenerating said one conventional carrier,

which inductor tuner exhibits inductance over the band of frequenciesthrough which said one conventional carrier is varied; a slug for saidinductor tuner; means for moving said slug relative to said inductortuner to change the amount inserted therein, thereby changing thefrequency of said one conventional carrier; the means for varying thefrequency of said other conventional carrier throughout a different bandof frequencies comprises a second inductor tuner in circuit with themeans for generating said other conventional carrier. which secondinductor tuner exhibits inductance over the band of frequencies throughwhich said second conventional carrier is varied; a second slug for thesecond inductor tuner; and means mechanicallycoupling said second slugto said means for moving the first mentioned slug to drive said secondslug relative to said second inductor tuner to change the amountinserted therein; thereby changing the frequency of said secondconventional carrier.

5. The transmitter of claim 4 wherein the means for modulating thecarriers comprises two separate sources of different frequency audiosignals; and bi-stable switching means for alternately applying signalsfrom said separate sources to modulate the conventional carriers.

6. The transmitter of claim 5 wherein the means for movm g said slugscomprises a reversible drive motor, stop limit switches, and powerconnections for the motor connected by the stop limit switches toreverse the motor drive, thereby to impart reciprocating motion to theslugs.

1. A proximity warning transmitter to be carried by an emergency vehiclefor transmission to conventional vehicle receivers comprising, incombination means for generating two conventional carriers of differentfrequencies; means for modulating one of the conventional carriers withaudio signals; means for modulating the other of said conventionalcarriers with said audio signals but in a different fashion; means forvarying the frequency of each conventional carrier throughout adifferent band of frequencies; and means for transmitting the modulatedvarying frequency carriers in a like predetermined direction relative tothe emergency vehicle.
 2. The proximity waRning transmitter of claim 1wherein the means for modulating the conventional carriers comprises twoseparate sources of different frequency audio signals; and switchingmeans for alternately applying signals from said separate sources tomodulate the conventional carriers and produce detectible audio warblecarried by each.
 3. The warning transmitter of claim 2 wherein the meansfor modulating said one conventional carrier comprises amplitudemodulating means; the means for modulating said other conventionalcarrier comprises frequency modulating means; and said switching meanscomprises bi-stable multivibrator means.
 4. The transmitter of claim 1wherein the means for varying the frequency of said one conventionalcarrier throughout a band of frequencies comprises an inductor tuner incircuit with the means for generating said one conventional carrier,which inductor tuner exhibits inductance over the band of frequenciesthrough which said one conventional carrier is varied; a slug for saidinductor tuner; means for moving said slug relative to said inductortuner to change the amount inserted therein, thereby changing thefrequency of said one conventional carrier; the means for varying thefrequency of said other conventional carrier throughout a different bandof frequencies comprises a second inductor tuner in circuit with themeans for generating said other conventional carrier, which secondinductor tuner exhibits inductance over the band of frequencies throughwhich said second conventional carrier is varied; a second slug for thesecond inductor tuner; and means mechanically coupling said second slugto said means for moving the first mentioned slug to drive said secondslug relative to said second inductor tuner to change the amountinserted therein; thereby changing the frequency of said secondconventional carrier.
 5. The transmitter of claim 4 wherein the meansfor modulating the carriers comprises two separate sources of differentfrequency audio signals; and bi-stable switching means for alternatelyapplying signals from said separate sources to modulate the conventionalcarriers.
 6. The transmitter of claim 5 wherein the means for movingsaid slugs comprises a reversible drive motor, stop limit switches, andpower connections for the motor connected by the stop limit switches toreverse the motor drive, thereby to impart reciprocating motion to theslugs.